Why did the u. s. army gunned down unarmed sioux at wounded knee creek, south dakota in 1890?

The U. S. army gunned down unarmed Sioux at Wounded Knee Creek, South Dakota, in 1890 primarily because the soldiers feared an uprising provoked by a militant interpretation of the Ghost Dance religion ... Americans by the thousands moved to the west in hope of striking gold, the promise of owning land, and farming.